Is it better to adjust offset with the inputs grounded and no resistors in the circuit or after installing resistors? Does adjusting offset after input and feedback resistors are included help make allowances for imperfect resistors?
If I change the op amp I would also certainly need to readjust offset. Do I need to if I change a resistor?

 

1. HP1729 "Is it better to adjust offset with the inputs grounded and no resistors in the circuit or after installing resistors?"

You should adjust the offset after all of the parts are connected, that way you will also compensate some of the offset that results in input bias current flowing through the resistors.

HP172: Does adjusting offset after input and feedback resistors are included help make allowances for imperfect resistors?
​

Not really with good resistors. I suppose in very small signal circuits thermo-electric effects such as at solder joints could be considered "imperfect resistors".

HP172: If I change the op amp I would also certainly need to readjust offset. Do I need to if I change a resistor?
​

It is a good idea and probably necessary for most opamps and applications.

 

1. HP1729 "Is it better to adjust offset with the inputs grounded and no resistors in the circuit or after installing resistors?"

You should adjust the offset after all of the parts are connected, that way you will also compensate some of the offset that results in input bias current flowing through the resistors.

HP172: Does adjusting offset after input and feedback resistors are included help make allowances for imperfect resistors?
​

Not really with good resistors. I suppose in very small signal circuits thermo-electric effects such as at solder joints could be considered "imperfect resistors".

HP172: If I change the op amp I would also certainly need to readjust offset. Do I need to if I change a resistor?
​

It is a good idea and probably necessary for most opamps and applications.

Thanks.